Long‐Term Wheel Traffic Effects on Soil Physical Properties under Different Tillage Systems

This study determined the effects of long‐term vehicular wheel traffic on soil physical properties for a Mattapex silt loam (fine‐loamy, mixed, mesic Aquic Hapludult) under different tillage systems. The site utilized a randomized complete‐block design with four replications of continuous‐corn ( Zea mays L.) plots under no‐till and conventional till, both of which had controlled wheel traffic for 14 yr. Wheel‐traffic loads during the 14‐yr period had been confined to axle loads of <4.5 Mg. Wheel traffic generally increased bulk density and soil strength. Wheel traffic resulted in over a 50% increase in soil strength when compared with non‐wheel‐tracked areas. The relative soil strength increase from wheel traffic was less for no‐tilled soil than conventionally tilled soil, although the mean increase (∼40 kPa) was the same for both tillage systems. Wheel‐traffic effects on bulk density and soil strength decreased with depth and were largely dissipated by the 30‐cm depth. The presence of wheel traffic in the conventionally tilled interrows significantly reduced the pore volume of pores >15 µm in the upper 17.8‐cm portion of the soil, but did not cause similar reductions in the no‐tilled interrows. Conventionally tilled soil exhibited more pore space in the 15‐ to 0.1‐µm radius range that should retain plant‐available water. Wheel traffic did not exhibit statistically significant effects for the 15‐ to 0.1‐µm range. Neither tillage system nor wheel traffic adversely changed soil physical properties so much that detrimental conditions for plant growth would be encountered. Reasonable doubt exists regarding the necessity to subsoil this soil on a regular basis to alleviate the effects of wheel traffic or continuous no‐tillage management as long as small‐scale farm equipment has been used.